1. Field of the Invention
This invention relates to probe pin assemblies for use in the electric measurement of semiconductor integrated circuit chips and liquid crystal devices, more specifically, to a probe pin assembly for use in testing integrated circuits on a wafer.
2. Description of Prior Art
Conventionally, the electric properties of a chip such as an IC chip and LSI chip are measured by contacting probe pins to the chip terminals for electric continuity. Cantilever type probe pins and perpendicularly movable pins are typical examples. In the cantilever type probe pin assembly, the probe pins are arrayed horizontally over the substrate and the pin ends are connected to the circuit pattern on a substrate. In the perpendicularly movable probe pin assembly, the probe pins are mounted vertically on the substrate and their output ends are connected to the circuit pattern on the substrate. Both types of pin probe assemblies adopt the beam structure to provide a contact pressure between the input unit and the terminals of the chip under test.
FIGS. 1-3 show examples of such probe pin assemblies. Referring to FIGS. 1, 26 and 27, a rectangular LSI chip 1 is exemplified as the chip 1 under test. The LSI chip 1 has electrode pads 2 in one or more than one line on its peripheral areas. For simplicity of drawing, the figures show only one line of electrode pads: five pads in the vertical direction and eight pads in the lateral direction.
Referring now to FIG. 1, the probe pin assembly 41 has a plurality of probe pins 42. Each probe pin 42 is a cantilever type pin, having an input unit 43 in one end, an output unit 44 in the other end and a deformation unit 45 of the cantilever structure between the input unit and output unit. The probe pins 42 are arrayed in accordance with the array of the electrode pads 2 of the LSI chip 1 around its peripheral areas. The probe pins are mounted on a substrate (not shown), and the output unit 44 is connected to a circuit pattern of the substrate.
The LSI chip 1 is mounted on an inspection bed (not shown) when the LSI chip 1 is tested or inspected. The LSI chip 1 is placed on the inspection bed in the form of a wafer that has not been diced into individual LSI chips. As the inspection bed is moved upward, the input unit 43 of each probe pin 42 resiliently contacts each electrode pad 2 of the LSI chip 1. Electric continuity is thereby established between the input unit 43 of the probe pin 42 and the electrode pad 2, and then the electric properties are measured.
The prior art probe pin assembly, however, has a problem that the probe pins do not reach all the electrode pads of the LSI chips together when a number of chips are arranged close to each other on a wafer as is the case where a plurality of LSI chips are arranged in a grid pattern on the wafer. This is because the probe pins of a predetermined length are arranged over each chip under test to occupy its peripheral spaces.
Moreover, as the IC manufacturing technology is improved these years, the circuit pattern has become extremely fine and the required pin pitch of probe pins used in IC testing has also become very small. As connectors that couple electronic devices together are also downsized, the terminal pitch thereof is required to be small as well. Then it becomes difficult to provide a probe pin having an appropriate spring constant because the probe pin is not allowed to have a sufficient space needed for the installation of its deformation unit. If the elastic deformation of a probe pin and its movable margin become small, an appropriate contact pressure is not provided between the probe pin and the electrode pad when there is, for example, a pin manufacturing error or a mechanical pin positioning error during contact.